Charge forming device and solenoid valve

ABSTRACT

A fuel and air charge forming device, such as a carburetor, may include a main body, a fuel and air mixing passage in the body, a fluid passage communicating with the fuel and air mixing passage and a solenoid valve. The solenoid valve may include a coil and a valve body having a base fixed against movement and a valve head extending from the base. The valve head may be driven by the coil between a first position wherein the valve head at least partially obstructs the fluid passage and a second position wherein the valve head permits greater fluid flow in the fluid passage to control fluid flow through the fluid passage.

TECHNICAL FIELD

This disclosure relates generally to a fuel and air charge formingdevice and a solenoid valve assembly.

BACKGROUND

Carburetors are used to provide fuel and air mixtures for a wide rangeof two-cycle and four-cycle engines, including hand held engines, suchas engines for chain saws and weed trimmers, as well as a wide range ofmarine engine applications, for example. Diaphragm-type carburetors areparticularly useful for hand held engine applications wherein the enginemay be operated in substantially any orientation, including upside down.Float bowl carburetors are typically used in applications wherein theyare not inverted like in lawn mowers, tractors and the like. In anattempt to achieve more efficient operation and to reduce exhaustemissions from engines, valves have been used to regulate the fuel andair mixture during at least some operating conditions.

SUMMARY

A fuel and air charge forming device, such as a carburetor, may includea main body, a fuel and air mixing passage in the body, a fluid passagecommunicating with the fuel and air mixing passage and a solenoid valve.The solenoid valve may include a coil and a valve body having a basefixed against movement and a valve head extending from the base. Thevalve head may be driven by the coil between a first position whereinthe valve head at least partially obstructs the fluid passage and asecond position wherein the valve head permits greater fluid flow in thefluid passage to control fluid flow through the fluid passage.

A solenoid valve may include a coil body, a coil surrounding at least aportion of the coil body to generate a magnetic field when energized,and a valve body. The valve body may have a base fixed against movementand a valve head extending from the base. The valve head may be drivenfrom a first position to a second position by the magnetic fieldproduced by the coil when the coil is energized and the valve head maybe resilient so that it returns to its first position when the coil isno longer energized.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of preferred embodiments and bestmode will be set forth with reference to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of one implementation of an exemplarycarburetor including a solenoid valve;

FIG. 2 is a cross sectional view of a main body of the carburetor ofFIG. 1 showing the solenoid valve;

FIG. 3 is a an enlarged, fragmentary, sectional view of a portion of thecarburetor of FIG. 2 showing the solenoid valve in an open position;

FIG. 4A is a perspective view of a valve body of the solenoid valve;

FIG. 4B is a side view of the valve body of FIG. 4A;

FIG. 5 is a perspective view of an exemplary float bowl carburetor;

FIG. 6 is a cross sectional view of the carburetor of FIG. 5;

FIG. 7 is a diagrammatic perspective view of a main body of an exemplaryfloat bowl carburetor including a solenoid valve;

FIG. 8A is an enlarged, fragmentary, side view of a portion of thecarburetor of FIG. 7 and showing the solenoid valve in a closedposition;

FIG. 8B is a view similar to FIG. 8A showing the solenoid valve in anopen position; and

FIG. 9 is a perspective view partially in section of a solenoid valvehaving an alternate valve head.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring in more detail to the drawings, FIGS. 1-3 illustrate a fueland air charge forming device, such as a carburetor 10, having asolenoid valve 12, a main body 14 with a fuel and air mixing passage 16extending therethrough (FIGS. 3 and 4) and having a throat or venturiportion 17 therein. The carburetor 10 may be a diaphragm-typecarburetor, having a fuel pump, and a fuel metering assemblycommunicating with an outlet of the fuel pump through a diaphragmcontrolled valve, as disclosed in U.S. Pat. No. 6,267,102 to Pattullo etal, incorporated herein by reference in its entirety. The fuel pumpdraws fuel from a fuel source such as a fuel tank and delivers it to afuel metering chamber 18 (FIGS. 2 and 3) that communicates with the fueland air mixing passage 16 through a needle valve 20 and a pair ofpassages 22, 24. One of the passages 22 preferably operates as an airbleed and/or fuel feed passage, depending on the orientation of athrottle valve 26 within the fuel and air mixing passage 16, asdiscussed in more detail hereafter, while the other passage 24 operatesprimarily as a fuel and air passage.

Still referring to FIGS. 2 and 3, the body 14 has a fluid passage, shownhere as an air bleed passage 28 communicating a portion of the fuel andair mixing passage 16 upstream of the venturi 17 with a portion of thefuel and air mixing passage 16 downstream of the venturi 17. The airbleed passage 28 extends through at least a portion of the body 14,shown here as extending from the fuel and air mixing passage 16 upstreamof the venturi 17 to a cavity 30 that extends to an outer surface 32 ofthe body 14. The air bleed passage 28 extends from the cavity 30 to afuel pocket 34 that is in communication with the passages 22, 24.Accordingly, when the throttle valve 26 is in an at least partially openposition (rotated from the idle or closed position shown in FIG. 2) theair bleed passage 28 communicates with the fuel and air mixing passage16 downstream of the venturi 17 through both passages 22, 24, and whenthe throttle valve 26 is in its closed or idle position (FIG. 2) the airbleed passage communicates with the fuel and air mixing passagedownstream of the throttle valve 26 via the passage 24.

The cavity 30 extending into the body 14 communicates one portion of theair bleed passage 28 upstream of the cavity 30 with another portion ofthe air bleed passage 28 downstream of the cavity 30. A base 36, or aportion thereof, may define a valve seat 38 through which the air bleedpassage 28 passes. Of course, the valve seat may be disposed at someother location along the air bleed passage 28, including at an end ofthe passage 28.

As shown in FIGS. 2 and 3, the solenoid valve 12 has a coil body 40, awire coil 42, a shell 44 and a valve body 46. The coil body 40 may beconstructed from a magnetically conductive metal material with a centralcore 48 that may be generally cylindrical and first and second end walls50, 52 at opposite ends of the core. One such material could be a coldrolled steel such as 12L14 utilized for the coil body 40, central core48, and shell 44. The first end wall 50 may have a first radiallyoutwardly extending flange 53 and an axially extending portion 54. Theaxially extending portion 54 may extend radially outwardly from the core48 but be radially inwardly spaced from the radially outermost peripheryof the flange 53. The first end wall 50 may have a slot or a pair ofopenings 56 through the flange 53 or both the flange 53 and the axiallyextending portion 54. The second end wall 52 may be provided, at leastin part, in the form of a second radially outwardly extending flange.The end walls 50, 52 and core 48 define a bobbin about which the wirecoil 42 may be wound.

The wire coil 42 may include a continuous winding of copper wire (whichcould be single strand) with wire sizes generally ranging from 36 AWG to28 AWG depending on a desired number of coil winding turns, coilresistance, and desired inductance for a particular solenoidapplication. The wire typically has 1 or more layers of insulativecoating, such as polyurethane enamel or polysol to preclude copper wirewinding from touching adjacent turns or shorting by direct contact ofthe copper wire to the core 48. Ends 58 of the wire coil 42 may extendthrough the openings 56 in the first flange 53 so that they may beconnected to an appropriate driving circuit or other source of power.Exemplary electrical energy sources may include a battery, magneto orrelated energy storage circuit(s) (capacitive or inductive) which may bederived from the engine ignition or charging system.

The shell 44 may surround at least a portion of the wire coil 42, andmay be connected to one or both flanges 52, 53 of the coil body 40. Theshell 44 may help focus or control the magnetic field generated by thesolenoid 12 as well as shield the wire coil 42 from contaminants. Theshell 44 may be disposed closely adjacent to the wire coil 42, or an airgap may be provided between them. In the implementation shown, thesecond flange 52 is smaller than the first flange 53 and the shell 44may be coupled to or carried by the first flange 53 and spaced from thesecond flange 52. The shell 44 may be press fit or otherwise secured tothe axially extending portion 54 of the first end wall 50 and receivedbeneath the first flange 53. The outer surface of the shell 44 may beradially flush with the periphery of the first flange 53. The outersurface of the shell 44 may be formed in stepped fashion providingdifferent diameter portions that may facilitate seating and sealing thesolenoid in a cavity of a body, like the cavity 30 in the carburetorbody. For example, each step may provide a shoulder that may directlyengage the carburetor body or a seal, such as an o-ring, to seal thecavity when the solenoid valve 12 is installed. The solenoid valve 12may also be positioned adjacent to the carburetor body 14 instead ofbeing received at least partially within a cavity of the body 14.

The valve body 46 may be constructed from or include a materialresponsive to a magnetic field, such as steel, and may be providedadjacent to the second end wall 52 of the coil body 40. At least aportion of the valve body 46 may overlie one or more fluid passages andmay be driven between a first position to at least partially obstructflow through or out of a fluid passage and a second position permittinga relatively free fluid flow through or out of the fluid passage. Forexample, the valve may control fluid flow through the air bleed passage28 to control the application of air from the air bleed passage 28 tothe fuel and air mixture passage 16. Of course, the valve 12 may be usedto control flow through passages other than the air bleed passage 28, aswill be discussed in more detail herein.

In at least one implementation, the valve body 46 may be provided in theform of a flexible and resilient disc, strip, reed, plate or the like.The valve body 46 may be made from a thin, flat reed or shim stockspring steel that is magnetically conductive. One such industry examplemight be unalloyed and low alloyed steels, like Sandvik MaterialsTechnology, 20C, where the rolled steel material is processed to reducefatigue stress and facilitate increased durability for bending andimpact strength. As shown in FIGS. 2, 3, 4A and 4B, the valve body 46may have a base 60 that is carried by the carburetor body 14 or anotherportion of the solenoid valve 12, such as the coil body 40 or shell 44,or the base 60 may be carried by an another component. The base 60 maybe fixed against movement at a location spaced from the air bleedpassage 28. The valve body 46 may also include a valve head 62 thatoverlies and is movable relative to the air bleed passage 28 (or otherpassage being controlled). In the implementation shown, the solenoidvalve 12 is normally closed in that the valve body 46, in its normalstate or first position shown in FIG. 2, engages the valve seat 38 andcovers and closes a portion of the air bleed passage 28 to prevent or atleast inhibit the flow or air out of that passage 28. To move the valve12 to its second or open position, electrical power is supplied toenergize the coil 42 which generates an electromagnetic field thatflexes or bends the valve body 46 so that the valve head 62 movesrelative to the base 60 and away from the air bleed passage 28, as shownin FIG. 3. In the open position, the valve more readily permits fluidflow from the air bleed passage 28 to the fuel and air mixing passage16, and may permit a substantially unrestricted fluid flow. When thecoil 42 is no longer actuated, the resiliency of the valve body materialreturns the valve body 46 to its unflexed, closed position to inhibit orprevent fluid flow through and/or out of the air bleed passage 28.

In the implementation discussed, the only moving part of the solenoidvalve 12 is a portion of the valve body 46 including the valve head 62which moves relative to the fixed base—no springs, plungers or othermoving components are needed. Of course, a spring or other biasingmember may be provided to yieldably bias the valve body 46 to its closedposition (for example), if desired for improved sealing, response timeor other reason.

The valve body 46 may be formed in many shapes and sizes. In the exampleof FIGS. 2, 3, 4A and 4B, the valve body 46 has a generally rectangularbase 60 with one or more holes 64 to facilitate attaching the base 60 toanother body with one or more fasteners like screws 66 (FIG. 3), rivets,stakes, clips and the like. The valve body 46 may be connected toanother body in any suitable way, including welding, adhering, frictionfit, etc. A relatively narrow neck section 68 may interconnect the valvehead 62 and base 60. The neck section 68 may facilitate flexing of thevalve body 46 and the size (e.g. width, thickness) of the neck 68, aswell as the other portions of the valve body 46, may be calibrated orselected to provide a desired response or movement of the valve head 62under a given force or load. The valve head 62 may be of any shape andhave a surface area suitable to close the desired port(s) and/orpassage(s). The entire valve body 46 may have the same thickness, or thethickness may vary, as desired. The valve body 46 may be readily stampedfrom a thin sheet of material and may be planar or generally planar whennot flexed (e.g. it may be planar from the point of connection to thecarburetor body to the portion of the valve head overlying the ports orpassages), or it may be contoured or bent in its normal state (that is,the state in which the valve body is not acted upon by another forcelike that created when the coil is energized) and either partiallystraightened, completely flattened out or further bent when the coil isenergized. An exemplary alternate valve body shape and arrangement isshown in FIG. 9. In FIG. 9, the valve body 46′ is formed from a planar,rectangular strip of material although other shapes and arrangements maybe used. The valve body 46, 46′ may be formed from a single piece ofmaterial where the base and valve head are formed from the same piece ofmaterial, if desired, or they may be formed from more than one piece ofmaterial or from different materials. The valve body 46, 46′ may also beformed from multiple layers of the same or different materials, and themultiple layers may extend over all or only part of the valve body. Forexample, one layer may provide a seal, one layer may provide a desiredstiffness and one layer may provide a desired magnetic conductivity orattraction. Of course, more or less than the noted layers may be used,and the layers may have properties and/or functions different than thosenoted.

In use, when the coil 42 is actuated, the electromagnetic field of thecoil 42 overcomes the resistance of the valve body 46 to bend or flexand thereby moves the valve head 62 away from the valve seat 38 to openthe air bleed passage 28. When the coil 42 is not actuated and noelectromagnetic field acts on the valve body 46 (or none of sufficientstrength to flex the valve body 46), the resilient nature of the valvebody material automatically returns the valve body to its unflexedposition wherein the valve head 62 closes the air bleed passage 28 orother port(s) or passage(s) with which it is associated.

In operation, to move the valve body 46 between its retracted andextended positions, the solenoid valve assembly 12 may be in electricalcommunication with a controller, such as an engine control module 70(FIG. 1) to receive signals therefrom, or the solenoid valve 12 may bedriven by some other circuit or control based on any desired parameteror condition. The engine control module (ECM) 70 may be responsive to atleast one, and preferably a plurality of variables that can affect theinitial start-up and continued running performance of the engine, suchas whether the engine is running or not, throttle position, RPM,temperature, and any other variables that affect the starting andrunning engine performance. Accordingly, the ECM 70 can be preprogrammedto send an electric signal to the solenoid valve assembly 12 to actuatethe valve body 46, as desired, so that the carburetor 10 operatesefficiently, thereby providing an optimal starting and runningperformance of an engine of a vehicle incorporating the carburetor 10.

Generally, when the engine is turned off, the valve body 46 may be inits closed position. In its closed position, the valve body 46 closesoff the air bleed passage 28. Accordingly, when the engine is started,the fuel and air mixture in the fuel and air mixing passage 16 isrelatively rich since air is not channeled to or free to flow throughthe air bleed passage 28 to the fuel within the fuel pocket 34. Thericher fuel and air mixture discharged from the carburetor 10facilitates a cold start of the engine, and warming-up and initialstable operation of the engine.

When the engine speed reaches a predetermined RPM value or range, as maybe programmed within the ECM 70, the ECM 70 sends a signal to thesolenoid valve assembly 12 thereby energizing the coil 42. The coil 42provides a strong enough magnetic field to flex the valve body 46 to itsretracted or open position. Accordingly, the air bleed passage 28 isopened to allow air from the fuel and air mixing passage 16 upstream ofthe venturi 17 to flow into and through the fuel pocket 34, therebyproviding a leaner fuel and air mixture to the fuel and air mixingpassage 16 than when the air bleed passage 28 was closed. As such, theengine receives a leaner air and fuel mixture to optimize the runningperformance of the engine per the programmed instructions of the ECM 70.

Therefore, the ECM 70, pursuant to its preprogrammed instructions,operates to send electrical current to the solenoid valve assembly 12 tomove the valve body 46 between its opened and closed positions tocontrol the fuel and air mixture supplied to the engine to control therunning performance of the engine. For instance, while accelerating thevehicle, it may be desirable to enrich the fuel and air mixture toensure sufficient fuel is provided to the engine to support the increasein fuel demand during acceleration. Therefore, during acceleration, thesolenoid valve 12 may be in its closed position thereby closing off theair bleed passage 28 and preventing enleanment of the fuel and airmixture. On the other hand, when decelerating, and to avoid a so-calledrich come-down condition wherein more fuel is provided than is needed,the ECM 70 can send a signal to the solenoid valve assembly 12 to movethe valve body 46 to its opened position, thereby opening the air bleedpassage 28 to lean out the fuel and air mixture. As such, it should berecognized that depending on the preprogrammed instructions within theECM 70, the solenoid valve assembly 12 can be operated to move betweenits opened and closed positions to optimize the running performance ofthe engine. In addition, sensors can be employed to communicate with theECM 70 to communicate such things as the fuel and air ratio of exhaustemissions, the fuel and air mixture ratio in the fuel and air mixingpassage 16, the position of the throttle valve 26, and the like tofacilitate the optimal operation of the solenoid valve assembly 12 toprovide optimum engine running efficiency and performance.

The valve 12 could also be used to control application of a positive airpressure signal to a float bowl chamber 100 (FIG. 6) in a float bowlcarburetor 102, such as shown in FIGS. 5 and 6. In one implementation,the float bowl carburetor may include a main body 104 having a fuel andair mixing passage 106 extending therethrough, and a throttle valve 108disposed in the mixing passage and carried by a valve rotating devicesuch as a shaft 110 extending through the body and a lever 112 connectedto the shaft.

Referring to FIG. 5, the carburetor also may include a float bowl 114sealingly carried on the body 104 by a fastener 116, a fuel inletpassage 118, an inlet needle 120 in communication with the inletpassage, and a float 122 to urge the inlet needle closed when athreshold level of fuel exists in the float bowl. The body may include afuel nozzle 124 extending into the float bowl and including a nozzlepassage 126 and a restriction 128 to the limit mass flow rate of fuelinto the nozzle at a pressure differential across the restriction. Thenozzle passage 126 extends through the nozzle 124 and is in fluidcommunication with and between the float bowl chamber 100 and the mixingpassage 106.

The solenoid valve 12 may be constructed in the same manner previouslydescribed and may be carried adjacent to or by the carburetor body 104.Although not shown in this implementation, the carburetor 102 mayinclude a pocket in which at least part of the solenoid valve 12 isreceived. A bleed path or control passage 130 may communicate with theatmosphere and with the mixing passage 106 via the nozzle bore 126 ofthe main nozzle. The valve head 62 of the solenoid valve 12 overlies andcloses the control passage 130 to inhibit or prevent application of anatmospheric pressure signal to the float bowl chamber 100 via thecontrol passage.

When the solenoid valve 12 is energized, the valve head 62 is displacedto open the control passage 130. The atmospheric pressure signal fromthe control passage 130 reduces the differential pressure across thenozzle 124 established between the float bowl chamber 100 and enginemanifold vacuum (and any pressure drop caused by flow through theventuri portion of the mixing passage) with a corresponding change infuel quantity supplied through the main jet or restriction 128. In thisimplementation, opening the control passage 130 causes enleanment of thefuel and air mixture delivered from the carburetor 102. The solenoidvalve 12 may be cycled between its open and closed positions to controlthe fuel and air mixture ratio as desired to change engine combustionefficiency or for some other reason.

Instead of controlling an atmospheric pressure air bleed, the solenoidvalve 12 may be used in a float bowl carburetor 200 to open and close apassage through which a subatmospheric pressure signal (sometimes calleda negative or vacuum pressure) may be provided from, for example, amixing passage 202 to a float bowl 204, as shown in FIGS. 7, 8A and 8B.In this regard, opening the solenoid valve 12 would provide an increasedpressure differential across a nozzle (not shown) to provide more fuelflow through the nozzle and delivery of an enriched fuel and air mixturefrom the carburetor 200. In the implementation shown in FIGS. 7, 8A and8B, a carburetor main body 210 includes the fuel and air mixing passage202 and a pressure signal passage 212 may be provided open to the fueland air mixing passage 202 downstream of a throat or a venturi 214 inthe fuel and air mixing passage. Accordingly, a pressure drop generatedat or by the venturi is communicated with the pressure signal passage212. The pressure signal passage 212 leads to the solenoid valve 12 andthe valve head 62, when closed, inhibits or prevents communication ofthe pressure signal from the pressure signal passage 212 to the floatbowl 204. However, when the valve head 62 is open (i.e. the valve head62 is displaced from its valve seat), then the pressure signal passage212 is communicated with a transfer passage 216 that is open to thesolenoid valve 12 at one end and communicates with the float bowl 204 atits other end via a suitable passage or conduit. In this way, thesubatmospheric pressure generated in the fuel and air mixing passage 202can be communicated with the float bowl 204 (such as to an air spaceabove liquid fuel in the float bowl) through the pressure signal passage212, the solenoid valve 12 and the transfer passage 216. The transferpassage 216 may join or otherwise communicate with an atmosphericreference passage which provides air at atmospheric pressure to thefloat bowl 204. In this way, the reference passage may be open to thefloat bowl 204 in any position of the solenoid valve 12 to reference thefloat bowl 204 to atmospheric pressure. Accordingly, when the solenoidvalve 12 is open, a reduced pressure is provided to the float bowl 204.

In at least some applications, there may be very little fuel flowrequired at engine idle and so there is a relatively low pressuredifferential on the fuel in the float bowl 204. Because of this, it maybe relatively difficult to control idle fuel flow by application of asubatmospheric pressure signal on the fuel in the float bowl 204.Further, the pressure at the pressure signal passage 212 may not besignificantly subatmospheric at idle. With this in mind, an air bleedpassage 220 can be used to partially or entirely diminish anysubatmospheric pressure signal that may be communicated to the floatbowl 204 when the solenoid valve 12 is open and the engine is idling ornearly so. A suitable restriction (not shown) may be provided in the airbleed passage 220 to control the flow rate therethrough (e.g. to preventundue dilution of the subatmospheric pressure signal at higher enginespeeds and loads).

By way of another non-limiting example, the solenoid valve 12 could alsobe used in a charge forming device such as a carburetor to control flowthrough or from a supplemental fuel passage that, when open, providesadditional fuel to the fuel and air mixing passage to enrich the fueland air mixture provided to the engine. This may be desirable, forexample, to assist engine acceleration. Of course, normal engineoperation could be obtained with fuel from the supplemental fuel passagebeing provided and, in that case, closing the supplemental fuel passagewould cause an enleanment of the fuel and air mixture, when desired.

The valve 12 could also be used to control the application of a reducedpressure signal (e.g. vacuum) or a positive air pressure signal to afuel metering chamber in a diaphragm carburetor where the pressuresignal would act on a fuel metering diaphragm of the carburetor. Stillother exemplary float bowl and diaphragm carburetors of this type aredisclosed in U.S. Patent Application Ser. No. 61/094,973, filed on Sep.7, 2008, assigned to the same assignee of this present disclosure, andincorporated herein in its entirety by reference. These carburetors canbe configured to use a solenoid valve of the type disclosed herein,rather than the solenoid valve disclosed in the above noted application.

It is to be understood that the foregoing description is not adefinition of the invention but is a description of one or morepreferred exemplary embodiments of the invention. The invention is notlimited to the particular embodiment(s) disclosed herein but rather isdefined solely by the claims below. Furthermore, the statementscontained in the foregoing description relate to particular embodimentsand are not to be construed as limitations on the scope of the inventionor on the definition of terms used in the claims, except where a term orphrase is expressly defined above. Various other embodiments and variouschanges and modifications to the disclosed embodiment(s) will becomeapparent to those skilled in the art. All such other embodiments,changes, and modifications are intended to come within the scope of theappended claims.

As used in this specification and claims, the terms “for example”, “forinstance,” and “such as,” and the verbs “comprising,” “having,”“including,” and their other verb forms, when used in conjunction with alisting of one or more components or other items, are each to beconstrued as open-ended, meaning that the listing is not to beconsidered as excluding other, additional components or items. Otherterms are to be construed using their broadest reasonable meaning unlessthey are used in a context that requires a different interpretation.

1. A fuel and air charge forming device, comprising: a main body; a fuel and air mixing passage in the main body; a fluid passage communicating with the fuel and air mixing passage; a solenoid including a coil and a valve body having a base fixed against movement and a valve head attached to and extending from the fixed base, wherein the valve head is driven by the coil between a first position wherein the valve head at least partially obstructs fluid flow through the fluid passage and a second position wherein the valve head permits greater fluid flow in the fluid passage to control fluid flow through the fluid passage.
 2. The device of claim 1 wherein the valve head inhibits fluid flow through the fluid passage when the valve head is in its first position and the valve head more readily permits fluid flow through the fluid passage when the valve head is in its second position.
 3. The device of claim 1 wherein the valve body is formed from a single piece of material with the base fixed to the main body and the valve head extending from and connected to the base, and the valve body is flexed by the force provided by the coil when the coil is energized to move the valve head to its second position and the valve head returns to its unflexed and first position when the coil ceases to be energized.
 4. The device of claim 1 wherein the valve body is a flat and planar piece of material when not acted upon by the energized coil and includes at least a portion that is magnetically receptive.
 5. The device of claim 1 wherein the valve body includes a neck section between the base and the valve head and the neck section is narrower than at least one of the base or the valve head.
 6. The device of claim 1 wherein the base is fixed to the main body.
 7. The device of claim 1 wherein the fluid passage includes an air bleed passage through which a supply of air may be selectively provided to the fuel and air mixing passage.
 8. The device of claim 1 wherein the fluid passage includes a fuel passage through which a supply of fuel may be selectively provided to the fuel and air mixing passage.
 9. The device of claim 1 wherein the fluid passage includes a control passage through which a pressure signal may be selectively provided to the fuel and air mixing passage.
 10. The device of claim 9 wherein the control signal is at a subatmospheric pressure.
 11. The device of claim 1 which also comprises a throttle valve in the mixing passage, a fuel pump carried by the main body, and a diaphragm controlled valve communicating with a fuel outlet of the fuel pump and the fuel and air mixing passage.
 12. The device of claim 1 which also comprises a fuel float bowl carried by the main body, a float received in the float bowl, and a valve opened and closed by the float to control admission of fuel into the float bowl.
 13. The device of claim 12 wherein the fluid passage communicates with the float bowl.
 14. The device of claim 13 which also comprises at least one passage communicating fuel in the float bowl with the fuel and air mixing passage.
 15. The device of claim 1 wherein the valve body is formed from a single piece of material that may be flexed by the force provided by the coil when the coil is energized to move the valve head and the valve body returns to its unflexed position when the coil is no longer energized.
 16. The device of claim 15 wherein the valve body is a flat piece of material when not acted upon by the energized coil and includes at least a portion that is magnetically receptive.
 17. The device of claim 15 wherein the valve body includes a neck section between the base and the valve head and the neck section is narrower than at least one of the base or the valve head. 